This application relates to centrifugal pumps and in particular to centrifugal pumps for pumping liquid in an automatic washer.
In particular this invention relates to a quick priming centrifugal pump which reduces or eliminates air or "suds" lock.
Automatic washers utilize pumps for draining the water out of the tub at the end of a washing cycle. The liquid solution of water and detergent, including soap suds, normally present in the tub is thus pumped to the drain. When the pump is first started, or when pumping soap suds near the end of a drain cycle when very little water remains in the tub, the rotating pump impeller will tend to create a vortex inside the inlet of the pump. The vortex is composed of a central pocket consisting primarily of suds or air, which pocket is located within a circulating layer of liquid which surrounds the central air pocket. When this condition occurs, the impeller, which is in communication with the air pocket, will unsuccessfully attempt to pump the air against the head of liquid present in the pump outlet. Pump flow will thereby be severely restricted. This condition is commonly known as "suds lock". If this condition occurs even to a small extent when the pump is first started, the pump priming time may be unacceptably long, which may cause the washing cycle to be unduly long or whereby, in washing machines with a fixed time washing cycle, all of the water may not be expelled or drained from the tub.
U.S. Pat. No. 4,087,994 discloses a centrifugal pump with means for precluding air lock wherein the impeller of the pump includes finger-like projections on each blade which extend radially outwardly from the impeller body into the outer annulus of the pumping chamber. These projections cut through the liquid which has been centrifuged to the outer annulus, thus causing a turbulence which draws a portion of the liquid into the body of the impeller for mixing with trapped air. This mixing action causes the air to be centrifuged with liquid and alleviates air lock in the pump. However, it should be noted that the vortex formed at the inlet of the pump is not reduced in size or eliminated.